Web stretching method and apparatus



INVENTOR.

April 11, 1961 K. w. MAlER WEB STRETCHING METHOD AND APPARATUS 2 Sheets-Sheet 1 Filed April 29, 1959 KARL W. MAIER April 11, 1961 K. w. MAIER WEB STRETCHING METHOD AND APPARATUS 2 Sheets-Sheet 2 Filed April 29, 1959 IFIIG=6 INVENTOR. KARL W. MAIER BY WEB STRETCHING METHOD AND APPARATUS Karl W. Maier, Cheshire, Conn., assignor to Olin Mathiason Chemical Corporation, a corporation of Virginia Filed Apr. 29, 19 59, Ser. No. 809,784

6 Claims. (Cl. 181) The present invention relates to Web processing methods and apparatus and, in particular, the invention relates to a method and apparatus for stretchinga web or film uniformly across its width.

A notable feature of the present invention is that the stretching method and apparatusdoes not embrace grasping the film or web solely along its edge or marginal regions.

The invention also contemplates stretching a web or film longitudinally, if desired.

A further feature of the invention is the provision of a method of stretching a film or web uniformly across its width, while in motion, where one increment of width of the web is elongated to the same extent as every other increment of width.

A further feature of the inveniton is the provision of a novel apparatus for practicing the method of the present invention.

A still further feature of the invention is the provision of a rotatable sheave or pulley characterizing a frame where the periphery of the frame which contacts the web carries an extensible member in the form of a resilient skin or in the form of a plurality of individual extensible elements.

A web stretching apparatus embracing certain features of the present invention may comprise a drum formed with a cam track, a cylindrical frame mounted concentrically with respect to said drum and movable relative thereto, said frame carrying a resilient or extensible means, cam followers connected to said member and in contact with said cam track so that as said frame moves relative to the drum the extensible means extends and retracts in accord with the contour of the cam track.

A method of stretching the web practiced by the operation of the apparatus of the invention and embracing certain features thereof may comprise the steps of passing the web about a rotatable sheave, the exterior surface of said sheave having a resilient or extensible means, establishing frictional contact between the Web and the sheave, progressively stretching or elongating the resilient means While the web traverses the sheave so that as the resilient means elongates axially the frictional contact between the web and the sheave is effective to stretch the web laterally and uniformly across the width thereof.

Other features and advantages will become more apparent from the succeeding specification when read in conjunction with the appended drawings, wherein:

Fig. 1 is a perspective view of an apparatus embracing the principles of the invention.

Fig. 2 is a development of the cam track formed upon the drum of Fig. 1. This figure also shows a portion of a skin-like extensible member.

Fig. 3 is a portion to the left side of Fig. 1, somewhat enlarged, to show the'detail of cam track, cam follower and the tube-like extensible member.

Fig 4 is a sectional view of a portionrof the left side of the cage of Fig. 1 showing the relationship between 2 theextensible tube, the cam follower and the supporting rod. a

Fig. 5 is an alternative embodiment of the invention utilizing an elastic belt, and,

Fig. 6 shows how the belt is clamped to the cam follower.

Referring now to the drawings, there is shown a pair of uprights 10 and 11 each. bored toreceivethe opposite ends of a shaft 12. The shaft 12, keyed .to the uprights to preclude rotation carries a drum 13 in turn keyed to the shaft to prevent rotation.

It is preferred that the drum and the shaft be keyed by releasable means, such as by set screws,.to facilitate phasing the drum with respect -to the uprights for reasons that will become more apparent hereinafter.

The periphery of thedrum is formed with a cam track indicated generally by the reference numeral 14 and includes cam slots 16 and 17 shown in developed formin Fig. 2.

The drum is enclosed by a cage or frame 18 which for purposes of claiming may sometimes be referred to as a squirrel cage-like structure.

The periphery-of thecage is characterized by an-ex tensible or resilient means operative to expand and contract along a path generally parallel to the axis of .the shaft 12. V

The frame 18 includes a pair of hubs 19l9 (only one shown) rotatably supported by the shaft 12. The hub 19 shown in Fig. 1 includes a pulley 21 suitably groovedto receive a V-belt 22 in turn connected to a source of power (not shown) elfective to rotate the cage relative to the stationary drum.

which is free to expand or contract along the longitudinal axis of the bar.

In one embodiment of the invention disclosed the resilient means comprises a series of rubber tubes 27-27.

Each end of a given tube is suitably connected, as by gluing, to a follower 2? and the follower, in turn, makes a sliding connection with its corresponding cam slot as at 31 (see Figs. 3 and 4).

Note that in another embodiment of the invention the resilient means can take the form of an endless resilient belt or skin 20 (Fig. 2) encircling and carried by the frame 18 and having flexible chain-like followers 25-25 on the edges thereof for engaging the cam slots.

Thus, as the frame 18 rotates relative tothe drum 13 the followers 29-29 (or the followers 2525, as the case may be) at opposite ends of the rubber tubes traverse the cam slots 16 and 17 and the relative rotation between the cage and the drum is effective to expand and contract the tubes (or the resilient belt) in accordance with the pattern of Fig, 2.

In order to prevent the followers 3-29 from rotat ing about their respective bars 26 and thusrotating out of the cam slot individual to a given follower, each bar 26 is formed with a flat side as at 32 in Fig. 3.

Referring to Fig. 1, note that in operation of the ap-,

The drum is so disposed and keyed with respect to the uprights that the point of tangency of the web therewith must coincide with the narrowestgap. or space C (see Fig. 2) between cam slots'16 and 17. Thus, as'the frame 18 is rotated in synchronization with, the speed of ad- Vance of the web Wthe followers traverse the slots 16 and 17 and move away from one another. I This motion is eflective to elongate the tubes uniformly and the; tubes 27 by virtue of their frictional contact with the web, stretch the web laterally and uniformly across the Width of the web to establish a new Width B.

Note that one increment of Width of the web is stretched the same amount as any other increment of width thereof. After the frame has rotated past the tangent point of web discharge the-cam slots are operative to allow the rubber tubes to contract. As the tubes approach the tangent point of entry of the web upon the drum 1 3 they are fully contracted and are poised to repeat the process just described.

The skin 20 will extend and contract in the same fashion. 1

Obviously the present invention is not limited to the particular cam track contour shown nor is it intended that the invention be limited to the disclosed tube or belt structure of the resilient members.

The disclosed embodiment of the apparatus and process is presented in order to explain and not to limit the invention.

What is claimed is:

1. A web stretching device comprising a drum formed with a cam track, a cylindrical frame mounted concentrically with respect to said drum and movable relative thereto, said frame carrying resilient means, cam followers connected to said means and in contact with said cam track so that as said frame moves relative to the drum the resilient means is extended and retracted in ac.- cord with the contour of the cam track.

2. The device of claim 1 wherein the cam track comprises a pair of spaced cam slots.

3. The device of claim 1 wherein the resilient means comprises a plurality of rubber tubes.

4. The device of claim 1 wherein the frame is formed with a plurality of bars each carrying a resilient tube.

5. The device of claim 1 wherein the resilient means takes the form of an endless belt.

6. The device of claim 1 wherein the cam followers take the form of a flexible chain-like element.

References Cited in the file of this patent UNITED STATES PATENTS Pfeiffer July 8, 1958 

